Detection of Malingering in Psychiatric Unit and General Population Prison Inmates: A Comparison of the PAI, SIMS, and SIRS

Abstract

In this study, we compared the utility of three instruments, the Personality Assessment Inventory (Morey, 1991), the Structured Inventory of Malingered Symptomatology (Smith & Burger, 1997), and the Structured Interview of Reported Symptoms (SIRS; Rogers, Bagby, & Dickens, 1992) to detect malingering among prisoners. We examined 4 inmate samples: (a) prisoners instructed to malinger, (b) “suspected malingerers” identified by psychiatric staff, (c) general population control inmates, and (d) psychiatric patients. Intercorrelations among the measures for the total sample (N = 115) were quite high, and receiver operating characteristic analyses suggested similar rates of overall predictive accuracy across the measures. Despite this, commonly recommended cut scores for these measures resulted in widely differing rates of sensitivity and specificity across the subsamples. Moreover, although all instruments performed well in the nonpsychiatric samples (i.e., simulators and controls), classification accuracy was noticeably poorer when attempting to differentiate between psychiatric patients and suspected malingerers, with only 2 PAI indicators significantly discriminating between them.

Notes

¹Prior to completing any of the malingering measures, the participants completed a self-report measure of psychopathic traits that is not the focus of this study. For further details see Poythress et al. (2001) or Edens, Poythress, et al. (2001).

²We note that scores on NIM are one of the components that go into the scoring of MAL, and scores on RDF and MAL are both affected by several overlapping PAI scales (e.g., INF). Thus, these correlations are based on somewhat overlapping variables.

³We do not report positive and negative predictive power (PPP and NPP) statistics here because our initial research design was targeted toward recruiting 30 participants in each group, which ultimately resulted in an artificial base rate of malingering that approximated 50%. Unlike sensitivity and specificity (and, consequently, area under the curve values), PPP and NPP are highly dependent on the base rate of the criterion in the sample.

⁴Other than querying the psychiatrists as to whether the symptoms were inconsistent with their own observations or the observations of other staff members, we did not collect systematically any additional data regarding the extent to which the psychiatrists relied on collateral information when determining that examinees were malingering. As such, we cannot definitively conclude that such information was used in these evaluations.